This application is related to and claims priority of Japanese Patent Application No. 254646, filed in Japan on Sep. 8, 1999, which is expressly incorporated herein by reference in its entirety.
I. Field of the Invention
The present invention relates to a mounting structure for an outboard motor.
II. Description of the Related Art
In general, an outboard motor is mounted to the hull of a boat via a clamp bracket. Also, an outboard motor is, for example, attached to a clamp bracket at upper and lower points of the motor via two mounting devices (the upper one constituting a steering bracket).
The mounting devices are equipped with a left-right pair of mount units and arranged widthwise on the outboard motor. A mount gum portion, which may be made of an elastic material such as rubber, is provided in the mount units to reduce vibration transmitted to the hull of the boat from the engine.
Generally, among the mount units, the upper mount unit is, for example, attached to an engine holder, while the lower mount unit is attached to a drive shaft housing. The manner of mounting the mount unit (e.g., the upper mount unit) to the engine holder generally involves mounting a portion of the mount gum portion of the upper mount unit into a mount holder previously formed on the engine holder during the casting stage, and then, pressing the mount gum portion via the mount cover to secure the mount sum portion. Also, there are two ways in which the mount gum portion can be inserted into the engine holder. Namely, a method of insertion from the top side of the engine holder, and a method of insertion from the front of the engine holder.
It is desirable for the mount gum portion of the upper mount unit to be adjacent to the center of gravity of the entire outboard motor so as to absorb vibration from the engine sufficiently and also it is desirable that the right and left pitch is sufficiently narrow.
However, in the method whereby the mount gum portion of the upper arm unit is inserted into the mount holder formed on the engine holder from the front side of the engine holder, because a drive shaft is inserted between the right and left mount gum portions, it is difficult to make the right-left pitch of the mount gum portions narrow because the protective wall for the drive shaft becomes blocked.
Moreover, when a mount gum portion is to be located adjacent to the center of gravity of the entire of the outboard motor, the front-back direction of the cylindrical mount holder becomes long, machining becomes difficult, and sufficient capacity for the mount holder is not obtained owing to issues related to the draft when casting. As a result, the mount has become small-sized in some cases. Also, when the front-back direction of the mount holder becomes long, the configuration of the mount cover, which presses on the mount gum portion, will end up with a complex shape.
Furthermore, when the mount gum portion of the upper mount unit is inserted into the cylindrical mount holder from the front side of the engine holder, the mount holder becomes sealed airtight and there is no place for internal air to escape. As a result, it is extremely difficult to insert the mount gum portion, and when the mount gum portion is removed from the mount holder for maintenance, etc., negative pressure is then generated within the mount holder, and it becomes extremely difficult to remove the mount gum portion.
Conventionally, to solve the problems described above, some mount gum portions are formed with grooves on their outer peripheral surface. However, when a groove is formed in the mount gum portion itself, the spring constant changes and the vibration absorption property may be adversely affected. Also, because grooves may generate directivity in the mount gum, there are cases where assembly requires careful attention.
Also, when the upper mount unit is installed on the steering bracket, the mount bolt for the upper mount unit is inserted through a mount arm formed on the steering bracket and is fastened at the end of the mount bolt with a nut, the mount bolt is pressed with a hand or another implement, or a whirl-stop notch is provided in the mount bolt to prevent turning. However, this technique involves a number of problems, such as insufficient tightening torque, and a decrease in the strength of the mount bolt owing to the notch, etc.
The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the advantages and purposes of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
The present invention was made with the exemplary object of overcoming the above described disadvantages of the prior art by providing a mounting structure of an outboard motor for reducing vibration.
Another exemplary object of the present invention is to provide a mounting structure of an outboard motor that reduces the number of assembling processes and improves workability or the process of manufacturing such a mounting structure.
In order to solve the exemplary problems described above, the mounting structure for an outboard motor of the present invention is, as described herein, such that in an outboard motor equipped with an engine mounted on an engine holder and installed onto the hull of a boat via a mounting device, and equipped with a crankshaft disposed more or less vertically within the engine, rotational force of this crankshaft is transmitted to a propelling device via a drive shaft, the axis of the drive shaft is located at a position offset away from the axis of the crankshaft a little to the rear of the outboard motor, and a pair of right and left mount holders is formed adjacent to the center of gravity of the outboard motor within the engine holder. The mount units are inserted into these mount holders from the front side of the engine holder, the drive shaft is inserted between the mount holders, and the mount holders are formed at the closest possible position to clear the protective wall for the drive shaft.
Also, to resolve the exemplary problems described above, the mount units are inserted into the mount holders from the front side of the engine holder and secured on the engine holder by mount covers from the front side so as to be freely attached or removed, and the mount covers are formed into a right-left asymmetrical configuration so as to clear the protective wall of the drive shaft.
Further, to resolve the problems described above, an exemplary aspect of the present invention includes openings on the front side of the engine holder of the mount holders disposed a little behind the drive shaft.
Moreover, to solve the problems described above, the mount unit comprises a mount bolt, a stopper formed somewhere along the mount bolt, a hollow inner tube disposed around a portion of the mount bolt behind the stopper, the rubber gum portion winding around the periphery of this inner tube, and a back nut for fixing the inner tube and the mount gum disposed and at the rear end of the mount bolt. In addition, the mount unit is divided into a rear mounting portion and a front steering fixing portion bordering with the stopper, the mounting portion is formed by fixing the mount gum portion to the mount bolt prior to the stage at which the mounting device is attached and this mounting portion is fixed to the engine holder, whereupon the steering fixing portion is fixed to a bracket that is provided on the hull of a boat.
Furthermore, to solve the problems described above, the stopper, which is located somewhere along the mount bolt, is formed into a non-circular configuration, and a fit corresponding to the sectional configuration of the stopper is formed in the bracket provided on the side of a hull, the stopper of the mount bolt engages this fit and thereby stops the mount bolt from turning.
Still further, to resolve the problems described above, a reverse thrust rubber is mounted onto the back nut and a receiver is formed at the back of the mount holder to receive the reverse thrust rubber therein.
Also, to resolve the problems described above, a groove is formed at the bottom on the inner peripheral surface of the mount holder that extends in the front-rear direction up to the opening of the mount holder on the front face of the engine holder.
It is to be understood that both the foregoing general description and the following detailed description are only exemplary, and are intended to provide further explanation of the invention as claimed.